VENOMOUS ANIMALS OF THE SOUTHWEST

WHY TALK ABOUT VENOMOUS ANIMALS? SO THAT YOU’RE NEITHER OVERLY WORRIED…

NOR OVERLY… WELL, YOU KNOW Most rattlesnake bite victims are young men (18-28 yrs old) who are bitten while handling or provoking the snake.

How to avoid being bitten or stung Never handle venomous animals Never place your hands or feet anywhere you can’t see (and haven’t checked). For example: –Never step into or over bushes –Never reach up onto a rock or ledge –Always pick up rocks, wood, etc. carefully, making sure not to put fingers under the rock/wood, always lift it so that the rock/wood is between you and the potential animal, and always check underneath. It is best to use a tool to lift a rock/wood.

POISONOUS VS VENOMOUS? Poisonous animals possess toxins. –For example, this Sonoran Desert Toad produces and secretes toxins from glands on its skin. The toad’s toxins are able to kill dogs that bite the toad! e.g., Parotoid Gland

POISONOUS VS VENOMOUS? Venomous animals inject their toxins. –For example, this rattlesnake produces toxins in modified salivary glands then injects toxins through hollow fangs.

THE CHARACTERS: MILDLY VENOMOUS ANIMALS Non-life-threatening except by anaphylactic shock in those that are allergic. Wasps, bees, ants, most spiders, most scorpions, etc.

THE CHARACTERS: DANGEROUSLY VENOMOUS ANIMALS Life-threatening. Need to seek medical attention. Bark scorpion, black widow, brown spider, gila monster, coral snake, rattlesnakes.

TYPES OF VENOM Hemolytic: affects circulatory system (“hemo” = blood) by destroying blood cells and vessels. Symptoms include severe pain, swelling, discoloration, and local tissue death. Shock can occur. Example: most rattlesnakes. Rattlesnake bite picture source

TYPES OF VENOM Neurotoxic: affects nervous system (“neuro”). Symptoms may include local pain, headache, lethargy, paralysis and occasionally death by circulatory arrest or respiratory paralysis. Usually no swelling, discoloration, or tissue death. Examples include Black Widow, Scorpions, and Coral Snake.

TYPES OF VENOM Other: –Gila Monster toxin causes pain. –Brown (“Recluse”) Spider toxin destroys proteins, thus tissues. Likely brown spider bite

WHY BE VENOMOUS? 1.Subdue Prey: allows predator to reduce chance of injury and to eat larger prey. 2.Defense: protects animal from predators and other potential threats. 3.Digest Food: venom is modified saliva, produced by modified salivary glands. Most contain compounds that aid in digestion (thought to be the “original use” of venom).

WHY NOT BE VENOMOUS? 1.Takes Special Equipment: requires glands to produce toxins and often specialized apparatus for injecting venom (teeth, modified ovipositor, etc.). 2.Takes Energy and Materials: toxins are expensive to produce.

WAYS TO AVOID WASTING TOXIN Match amount of venom to prey: use less for smaller prey, use more for prey that can get away easier (e.g., birds).

AVOID USING TOXIN Hide (use cryptic coloration): camouflage. Warn (use aposematic coloration): bright, memorable colors and/or patterns.

AVOID USING TOXIN Retreat

ONE MORE WAY TO AVOID USING TOXIN Don’t produce toxins at all – be a Fake! –Batesian Mimics just pretend to be dangerous or inedible. Thus potential predators avoid them, but it doesn’t cost them.

Some useful terms Nocturnal: active at night (e.g., scorpions) Diurnal: active during daylight hours (e.g., gila monsters) Crepuscular: active during dawn and dusk (e.g., deer tend to be most active around sunrise and sunset)

DANGEROUSLY VENOMOUS ANIMALS: ARACHNIDS (8-legged) bark scorpion: of 30 AZ species of scorpion, only the bark scorpion sting is considered life-threatening. Identified by long, thin pincers. Climbs, is nocturnal, and is neurotoxic. Bark scorpion Stripe-tailed scorpion Compare pincer shapes

DANGEROUSLY VENOMOUS ANIMALS: ARACHNIDS (8-legged) “black widow”: Nocturnal, makes strong, messy web. Neurotoxic.

DANGEROUSLY VENOMOUS ANIMALS: ARACHNIDS (8-legged) “brown spider”: thin, spindly spider with three pairs of eyes in semicircle (difficult to see). May have violin-shaped marking on cephalothorax (“head”). Bite causes tissue damage. Compare to Wolf Spider which is not deadly marking

DANGEROUSLY VENOMOUS ANIMALS: REPTILES Gila monster : only other known venomous lizard in the world is Mexican beaded lizard (in Mexico). Diurnal, but spends 98% of time in burrow; peak activity in spring when hunting nestlings/eggs. Has “leaky” skin. Venom for defense (pain) only.

DANGEROUSLY VENOMOUS ANIMALS: REPTILES coral snake: member of cobra family. Has highly toxic venom but small fangs and mouth so difficult to bite humans. Nocturnal. Neurotoxic. Identified by the phrase: red and yellow kill a fellow (notice how red band touches yellow bands); versus red and black friend of Jack (non-dangerous snakes have red touching black).

DANGEROUSLY VENOMOUS ANIMALS: REPTILES Rattlesnakes: 11 species (17 subspecies) of rattlesnakes in Arizona

TRUE OR FALSE? You can tell the age of a rattlesnake by counting the segments of its rattle. Baby rattlesnakes are more dangerous. Rattlesnakes must be coiled to strike. Rattlesnakes always rattle before striking Rattlesnake eggs are good eating Rattlesnake bites are always fatal All False Source: AGFD

RATTLESNAKE SENSE ORGANS Eyes: to see Nostrils to smell Body to feel ground vibrations Pit Organ to sense heat Cont >>

RATTLESNAKE SENSE ORGANS Jacobson’s Organ to augment smell by analyzing chemicals brought to it by the tongue which picks up the chemicals from the air and ground.